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High-temperature polar clusters in perovskite-type relaxor ferroelectrics and their response to an electric field

钙钛矿型弛豫铁电体中的高温极性团簇及其对电场的响应

基本信息

批准号：
160898240
负责人：
Professorin Dr. Boriana Mihailova
金额：
--
依托单位：
Mineralogisch-Petrographisches Institut (MPI)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2012-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/160898240?language=en
关键词：
temperature polar clusters perovskite type

项目摘要

Relaxor ferroelectrics are locally inhomogeneous materials that have been attracted tremendous attention due to their exceptional dielectric, electromechanical and electrooptic response. The unique relaxor properties are related to the existence of polar nanoclusters dispersed in the overall cubic structure. The understanding of the actual polar atomic clustering and its interplay with the relaxor properties is a great challenge to condensed-matter physicists and materials scientists. This project aims to analyze the preferential polar atomic shifts and coupling processes to form polar nanoregions at temperatures above the temperature of the dielectric permittivity maximum. For the purpose, resonance Raman spectroscopy will be applied to model compounds (stoichiometric and Ba-doped PbSc0.5Ta0.5O3 and PbSc0.5Nb0.5O3) in the temperature range 670 – 80 K to analyze the evolution of the mean size and distribution of polar species via the changes in the enhanced longitudinal optical modes. Further, the same compounds will be studied by in situ conventional Raman spectroscopy under an external electric field at temperatures between 850 and 80 K to elucidate the preferred crystallographic direction of coherent polar atomic displacements and the switchability of polar clusters. In addition, the temperature evolution of phonon and valence-electron states of newly synthesized Ru-containing PbSc0.5Ta0.5O3, PbSc0.5Nb0.5O3 and 0.9PbZn1/3Nb2/3O3-PbTiO3 will be analyzed by Raman spectroscopy and optical ellipsometry.

弛豫铁电体是一种局部非均匀材料，由于其优异的介电、机电和电光响应特性而引起人们的极大关注。独特的弛豫性质与分散在整体立方结构中的极性纳米团簇的存在有关。对实际极性原子团簇及其与弛豫性质的相互作用的理解是凝聚态物理学家和材料科学家的一个巨大挑战。该项目旨在分析优先极性原子位移和耦合过程，以在高于介电常数最大值的温度下形成极性纳米区域。为此目的，共振拉曼光谱将被应用到模型化合物（化学计量和Ba掺杂的PbSc0.5Ta0.5O3和PbSc0.5Nb0.5O3）在670 - 80 K的温度范围内，通过增强的纵向光学模式的变化来分析极性物种的平均尺寸和分布的演变。此外，相同的化合物将研究原位常规拉曼光谱下的外部电场在850和80 K之间的温度，以阐明相干极性原子位移和极性集群的可切换性的优选结晶方向。此外，我们还利用拉曼光谱和椭圆偏振光谱分析了新合成的含Ru的PbSc_（0.5）Ta_（0.5）O_3、PbSc_（0.5）Nb_（0.5）O_3和0.9PbZn_（1/3）Nb_（2/3）O_3-PbTiO_3的声子态和价电子态的温度演化。